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Ambient temp reading low

TimN1987

New member
Location
Leeds
Car(s)
Golf 7.5R Estate
Hi, ambient temp on our mk7 1.6 TDI is reading low - always reading in the negative even when it isn't that cold. Have replaced the sensor and it persists. I have searched this forum and others to no avail.
No running problems, have just had the heating block and coolant system replaced but the ambient temp problem pre-dates that and doesn't seem related- this could have been going on for the last 6 months as it has been cold but now it's been nicer there is obviously something wrong.

Does anyone have any suggestions?
 

golfdave

Autocross Champion
Location
Scotland (U.K.)
Car(s)
Mk7 Golf GT Estate
So you've replaced the outside air temp sensor which sits behind the lower grille & you still have problems???..It could be the wiring..only way to really tell is to inspect the wiring & run a scan...
 

TimN1987

New member
Location
Leeds
Car(s)
Golf 7.5R Estate
So you've replaced the outside air temp sensor which sits behind the lower grille & you still have problems???..It could be the wiring..only way to really tell is to inspect the wiring & run a scan...
Yes replaced the sensor behind the grill, the old one wasn't evidently damaged and the new replacement reads the same. The wiring I can see before it dives under the flap and heads back towards the engine looks ok, will have a look at what else I can get to. It's very strange as when driving the temp does go up and down but nowhere near what the ambient temperature actually is (or what the other car says, which is also a golf). Doesn't seem to affect anything else, it's just annoying.
 

golfdave

Autocross Champion
Location
Scotland (U.K.)
Car(s)
Mk7 Golf GT Estate
Needs a scan to see that its not got any faults....
 

Cuzoe

Autocross Champion
Location
Los Angeles
I'm making an assumption that our cars use a thermistor type sensor. If the delta between actual and indicated temp is nearly the same all the time (and always low, as you said) I would check the resistance of the wiring between Sensor and BCM. The schematic doesn't show any disconnects between the sensor and BCM but high resistance can't be determined visually.

Temp Sensor Pin 1 ----> BCM Plug B Pin 19
Temp Sensor Pin 2 ----> BCM Plug B Pin 27

Note that BCM Plug B Pin 19 is a common ground also shared with other sensors, Washer Fluid Level and Engine Coolant Level. It shouldn't impact your checks. But you could also check the Washer Fluid Sensor plug to the BCM as a comparison point. Should read very close to the same and it's all in the same locations.

Washer Fluid Sensor Pin 1 ----> BCM Plug B Pin 19
Washer Fluid Sensor Pin 2 ----> BCM Plug B Pin 28
 
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